1. Field of the Invention
This invention pertains to novel water-compatible resinous compositions comprising one or more cationic compounds which comprise vinylized epoxy resins having at least one terminal unsaturated group and one terminal pyridinium salt group. This invention further pertains to the inclusion of said compounds in aqueous dispersions and to the use of such aqueous dispersions as coatings and adhesives.
2. Description of the Prior Art
The term "cationic compounds" embraces a variety of organic compounds which ionize in the presence of water to form a cation (i.e., a molecule bearing a positive electrical charge). This positive charge is almost always borne by a hetero atom of phosphorus, nitrogen or sulfur. In some instances, the positive charge has been borne by a combination of carbon atoms and hetero atoms (e.g., an isothiouronium group). Such positively charged portions of the molecules have an affinity for water and can render the molecules water-compatible, i.e., either water-soluble or water-dispersible; this property has caused such organic compounds to be the subject of intensive investigation and commercialization. A brief scan through any handbook on surfactants (e.g., McCutcheon's Detergents and Emulsifiers, North American Edition, 1977) will show the extent to which such compounds have been utilized.
Cationic compounds in which the positive charge is borne by a nitrogen atom are probably the best known and most widely used. Perhaps it is because of this wide usage, or because of the evolutionary nature of the technology, that the chemical nomenclature for such compounds has been abused and inconsistently used. Such compounds have been mistakenly referred to in much of the early literature as merely "quaternary ammonium" compounds. Quaternary ammonium compounds are compounds in which the nitrogen atom is bonded to four carbon atoms by way of four single covalent bonds.
There is a separate and distinct class of nitrogen-containing organic compounds which are referred to as aromatic heterocyclic amines. Aromatic heterocyclic amines have one (or more) nitrogen atoms as a member of a heterocyclic aromatic ring. Such aromatic amines are normally 5- or 6-membered rings. The 6-membered mononuclear heterocyclic ring systems containing one nitrogen atom are by far the more common and are generically referred to as pyridines. These aromatic amines can be alkylated to form pyridinium compounds as illustrated below: ##STR1##
Some elementary organic texts (and a few other technical writings) have included pyridiniums under the terminology "quaternary ammonium" compounds. Almost invariably, the point being made in such instances was that a pyridine is a nitrogen-containing organic base which can be protonated to form an acid/amine salt (e.g., a pyridine hydrochloride) even though the pyridines are much less basic. However, the organic chemist who is knowledgable regarding pyridines and pyridinium compounds will not be misled by such erroneous terminology because the chemical and physical properties of the compounds per se render them substantially different from the true quaternary ammonium compounds having four carbon atoms bonded to nitrogen by single covalent bonds.